Magnesium hydroxide nanoparticles, methods of making same and compositions incorporating same

Abstract

Magnesium hydroxide nanoparticles are made from a magnesium compound that is reacted with an organic dispersing agent (e.g., a hydroxy acid) to form an intermediate magnesium compound. Magnesium hydroxide nanoparticles are formed from hydrolysis of the intermediate compound. The bonding between the organic dispersing agent and the magnesium during hydrolysis influences the size of the magnesium hydroxide nanoparticles formed therefrom. The magnesium hydroxide nanoparticles can be treated with an aliphatic compound (e.g., a monofunctional alcohol) to prevent aggregation of the nanoparticles during drying and/or to make the nanoparticles hydrophobic such that they can be evenly dispersed in a polymeric material. The magnesium hydroxide nanoparticles exhibit superior fire retarding properties in polymeric materials compared to known magnesium hydroxide particles.

1. Fire retardant magnesium hydroxide particles, comprising:
 a plurality of magnesium hydroxide particles having an average diameter of less than 1000 nm, each magnesium hydroxide particle having one or more surface functionalizing molecules bonded thereto in a molar ratio of magnesium to functionalizing molecules of less than 100, the functionalizing molecules having the following formula:
   -L 1 -R 1 -L 2 -R 2    
 
 
       wherein
 L 1  and L 2  are linking groups independently selected from the group consisting of a hydroxyl, a carboxyl, a carbonyl, an amine, an amide, a nitrogen having a free lone pair of electrons, a hemiacetal, a carboxy thiol, a thiol, a sulfonic acid, a sulfonyl halide, an acyl halide, and derivatives thereof; and 
 R 1  and R 2  are independently a branched or unbranched, cyclic or acyclic, substituted or unsubstituted, saturated or unsaturated, or aromatic hydrocarbon having between 1 and 30 carbon atoms. 
 
     
     
       2. The magnesium hydroxide particles of  claim 1 , wherein the magnesium hydroxide particles are substantially free of water such that the particles form a dry powder. 
     
     
       3. A fire retardant composition, comprising the magnesium hydroxide particles of  claim 2  mixed with a polymerizable resin. 
     
     
       4. The magnesium hydroxide particles of  claim 1 , wherein L 2 -R 2  is a fatty acid, a silane, a titanate, an aluminate, an alum-titan, a monofunctional alcohol, a monofunctional carboxylic acid, or a derivative thereof. 
     
     
       5. A fire retardant composition, comprising the magnesium hydroxide particles of  claim 2  mixed with a polymeric material. 
     
     
       6. The fire retardant composition as in  claim 5 , wherein the polymeric material comprises at least one of a polyolefin or methyl methacrylate. 
     
     
       7. A method of manufacturing the fire retardant magnesium hydroxide particles of  claim 1 , the method comprising:
 (i) providing a plurality of magnesium atoms; 
 (ii) providing a plurality of organic agent molecules comprising at least one functional group selected from the group consisting of a carboxyl, a carbonyl, an amine, an amide, a nitrogen having a free lone pair of electrons, a hemiacetal, a carboxy thiol, a thiol, a sulfonic acid, a sulfonyl halide, an acyl halide, and derivatives thereof; 
 (iii) reacting the organic agent molecules with the magnesium atoms to form an intermediate magnesium compound; and 
 (iv) treating the intermediate magnesium compound with a base to form magnesium hydroxide particles. 
 
     
     
       8. A method as in  claim 7 , further comprising drying the magnesium hydroxide particles formed in step (iv) by mixing the particles with an organic solvent and evaporating the solvent. 
     
     
       9. A method as in  claim 7 , wherein the organic agent molecules comprise an aliphatic compound which is a monofunctional alcohol or an organic acid. 
     
     
       10. A method as in  claim 7 , wherein the solvent comprises butanol. 
     
     
       11. A method as in  claim 7 , wherein the organic agent comprises two or more different types of functional groups. 
     
     
       12. A method as in  claim 11 , wherein at least one of the two or more different types of functional groups is a hydroxyl group. 
     
     
       13. A method as in  claim 7 , wherein the organic agent molecules comprise one or more of glycolic acid, citric acid, glycine, alanine, ethanolamine, urea, mercaptoethanol, mercaptoacetate, sulfobenzyl alcohol, sulfobenzoic acid, or pyridine. 
     
     
       14. A method as in  claim 7 , wherein the magnesium hydroxide particles have an average diameter of less than about 500 nm. 
     
     
       15. A method as in  claim 7 , wherein the magnesium hydroxide particles have an average diameter of less than about 50 nm and agglomerate to form agglomerated particles of between about 100 nm and about 1000 nm. 
     
     
       16. A plurality of magnesium hydroxide nanoparticles manufactured according to the method of  claim 7 . 
     
     
       17. A composition comprising a polymeric material mixed with the nanoparticles of  claim 16 .